At present radio telecommunications networks mainly use digital signal transmission techniques. There are two main families of digital radiotelephone standards: mobile telephone standards for public cellular networks, such as the GSM, DCS and UMTS standards, and cordless telephone standards, such as the Bluetooth and DECT standards, enabling a cordless telephone to be connected to a fixed radio part connected to the fixed or “wired” network.
Standards such as the GSM standard have enabled widespread adoption of mobile telephones because they are user friendly and offer good call quality.
Similarly, cordless telephones to the DECT standard, for example, are increasingly popular with consumers because they allow users some freedom of movement.
To make the life of radiocommunications terminal users easier, it has been proposed to create multi-standard mobile terminals which can process calls in both families of standards without changing telephone handset. A multi-standard terminal then enables use of either a “mobile” link, i.e. a telecommunications link set up via a mobile telephone network, or a “fixed” link, i.e. a link set up via a fixed part of a preferred local network providing a direct connection to the public switched network.
Users can therefore use a fixed link when they are in the coverage area of a local network that the terminal can log onto, with the benefit of lower call charges.
By using a mobile link from the same handset, the user enjoys the advantages of the mobile network when moving around.
However, a problem with multi-standard terminals is how to define when to change from the fixed mode to the mobile mode and vice-versa, given that, to reduce call costs, the terminal should log onto a preferred local area whenever possible.
At present, two preferred local network search modes enabling a change to “fixed” mode are known in the art, namely an automatic mode and a manual mode.
In the automatic mode, the fixed part is searched for continuously, regardless of whether it is actually used or not. Thus the search is effected whether the terminal is in the coverage area of a preferred local network which it can log onto or not. This search for a fixed part leads to a high consumption of energy by the terminal, which considerably reduces its standby and talk times.
This problem is aggravated if the terminal is associated with a plurality of fixed parts, because it then searches continuously for all of them in the automatic mode. In the manual mode, the user switches the terminal from the “mobile” mode to the “fixed” mode or vice-versa. This is inconvenient for users, who must remember to switch mode each time they enter the coverage area of a preferred local network associated with their terminal. As the terminal can be used anywhere in the “mobile” mode, users can easily forget to switch to the “fixed” mode.